Upon this, the newly instated minister T'Pau began cleaning house, which resulted in many former High Command ships being undercrewed by the time of the Babel Crisis. During the incident, she was only able to dispatch twenty-three starships to add to the combined Andorian-Human-Tellarite intercept fleet. (ENT: "United")
A possible candidate for the role of successor to the High Command might be the Vulcan High Council mentioned in ENT: "These Are the Voyages...", which was apparently powerful enough to be responsible for the decision that Vulcan join the Federation.
This would imply that either the High Command was re-established in some form, or that Lorot was somehow assimilated before 2154, long before official first contact with the Borg. If the former, then Vulcan Space Central and the V'Shar might also operate under the authority of the High Command. It should be noted that Vulcan maintained its own fleet of ship separate from Starfleet as late as 2368, as seen in TNG: "Unification II"
This would imply that the High Command was either reinstated after 2233, the point of divergence, or it was reinstated in both universes. The latter possibility would facilitate Lorot being assimilated after first contact with the Borg.